The present invention relates generally to radar transmitting and receiving devices, and more specifically to systems for detecting obstruction material on or about a radar antenna carried by a motor vehicle.
Systems for tracking object position and/or velocity are well known and have been widely implemented in a variety of applications. Examples include, but are not limited to, tracking aircraft position, detecting motor vehicle speed and tracking both the position and velocity of a leading vehicle in an automotive adaptive cruise control and/or collision warning system.
Many such radar systems rely on the Doppler principle, where a radio frequency signal is transmitted by an antenna into space, and where at least some of the signal is reflected off an object back to the transmitter at a different frequency. The reflected radiation can then be processed to determine the velocity and/or position of the object relative to the transmitter. Additionally, many radar systems encode the transmitted frequency such that the reflected signal may be processed to determine the relative velocity of the object, the Doppler component, and the relative range of the object from the transmitter.
Typical radar systems used in motor vehicle applications include a radar antenna surrounded or encased by a protective radome. In conventional motor vehicle applications, the antenna/radome combination is mounted to the front of the vehicle; typically behind the front bumper or grill, in a forward-looking radar system application, or to the rear of the vehicle; typically behind the rear bumper, in a rearward-looking radar system. Mounted at such locations, the antenna/radome combination is accordingly susceptible to obstructions that may result in degraded, or even total loss of, system performance. Sources of such obstructions may include snow, slush, ice, mud and other debris, as well as radar signal impeding structural items mounted to the vehicle in line with one or more signal transmission/detection axes. In any case, it is important, if not imperative, that the radar system includes some type of mechanism for detecting radar obstruction or blockage.
Several approaches to detecting radar obstruction or blockage are known. For example, one conventional radar blockage detection technique includes calibrating the radar system using an external target of known reflectivity at a specified distance, and then periodically testing the system using this calibration technique. However, while this technique may work well for stationary systems or systems that can easily transport and accurately position an external target, it is impractical for use with a mobile platform for detecting obstructions in real time.
Another known radar blockage technique that is particularly useful with mobile platforms such as motor vehicles includes outfitting the radome with a grid or other pattern of electrical conductors. By measuring the electrical impedance of the grid, it is possible to determine with acceptable accuracy the presence of electrically conductive foreign matter that may have accumulated on the radome, such as ice, snow, slush and/or mud. However, this approach unnecessarily adds significant cost and complexity to the system in the form of both hardware and software. Moreover, this approach is limited to detection of radar blockage matter accumulated only on the radome itself, and is generally not operable to detect the presence of other blockage matter that may have formed elsewhere in the transmission/receiving path of the radar antenna.
What is therefore needed is an improved radar obstruction or blockage detection system that overcomes the foregoing drawbacks of known vehicular radar obstruction detection systems.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for detecting radar blockage comprises a radar unit having an antenna configured for transmitting radar signals and for receiving reflected radar signals, a vehicle speed sensor producing a vehicle speed signal indicative of a travelling speed of a vehicle carrying the radar unit, and a control computer responsive to at least some of the reflected radar signals to compute a relative radar power signal as a function of frequency, the control computer responsive to the vehicle speed signal to determine a mainbeam clutter peak of the relative radar power signal along a number of Doppler frequencies defined by the travelling speed, the control computer setting a first radar blockage flag if the mainbeam clutter peak is below a power threshold value.
In accordance with another aspect of the present invention, a system for detecting radar blockage comprises a radar unit carried by a motor vehicle, the radar unit having an antenna configured for transmitting radar signals and for receiving reflected radar signals, and a control computer responsive to the reflected radar signals to track at least one object external to the vehicle, the control computer normalizing corresponding tracking amplitudes of the reflected radar signals to a predefined tracking distance and filtering the normalized tracking amplitudes to produce a smoothed tracking amplitude, the control computer setting a first radar blockage flag if the smoothed tracking amplitude drops below an amplitude threshold value.
In accordance with yet another aspect of the present invention, a method for detecting radar blockage comprises the steps of transmitting a radar signal with a radar system carried by a motor vehicle, receiving reflected radar signals resulting from the transmitting step, processing the reflected radar signals to produce a relative power signal as a function of frequency, determining a mainbeam clutter peak of the relative power signal based on frequencies corresponding to those about a travelling speed of the vehicle, and setting a first radar blockage flag if the mainbeam clutter peak is below a power threshold value.
In accordance with a further aspect of the present invention, a method for detecting radar blockage comprises the steps of transmitting a radar signal with a radar system carried by a motor vehicle, receiving reflected radar signals resulting from the transmitting step, processing the reflected radar signals to track at least one object external to the vehicle, normalizing corresponding tracking amplitudes of the reflected radar signals to a predefined tracking distance, filtering the normalized tracking amplitudes to produce a smoothed tracking amplitude, and setting a first radar blockage flag if the smoothed tracking amplitude drops below an amplitude threshold value.
One object of the present invention is to provide a system for detecting blockage of a radar transmitting and receiving antenna forming part of a radar system carried by a motor vehicle.
Another object of the present invention is to provide such a system for detecting radar blockage by comparing the mainbeam clutter peaks of reflected radar signals with a predefined power threshold value.
Still another object of the present invention is to provide such a system for detecting radar blockage by comparing a smoothed, normalized tracking amplitude with a predefined amplitude threshold value.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.